Electronic line sectionalizers of this type are disclosed in U.S. Pat. No. 4,636,764--Mee et al and 4,553,188--Aubrey et al, both of which are incorporated by reference in the present application. The sectionalizer of the Mee et al patent includes overcenter toggle means which normally holds the sectionalizer in its closed-circuit position and actuating means which responds to a signal from the electronic control means to release the overcenter toggle means and thereby cause the sectionalizer to open. The sectionalizer opens only when the circuit therethrough is in an interrupted state and thus must rely upon stored energy to trigger the actuator into operation.
In the Mee et al patent, the actuating means is a chemical actuator in which a chemcial charge is detonated by a pulse of electrical energy derived by discharging a charged capacitor in the electronic control means. A disadvantage of this type of arrangement is that the chemical actuator is a one-shot device which must be replaced in the field after each such opening operation to permit the sectionalizer, following such opening, to be reset to its closed condition in readiness for continued operation in the same manner as described above.
Replacement of the actuator is a matter of some concern to users, first of all, because of the cost of the replacement actuator and, secondly, because of the need for the line crew to correctly connect the actuator to the electronic circuitry of the sectionalizer for reliable continued operation of the sectionalizer.
One prior approach to avoiding the need for actuator replacement after each actuator-produced opening operator of the sectionalizer is embodied in U.S. Pat. No. 4,795,996--Brown et al, which discloses a sectionalizer that comprises a linkage for holding the sectionalizer closed, which linkage is held in an undercenter position by a first releasable latch. For effecting opening of the sectionalizer, Brown et al provide an actuator that comprises a charged spring and a second releasable latch for holding the spring charged. The second latch is controlled by a solenoid which is operated by a pulse of electrical energy from the electronic control means. Release of the second latch by the solenoid allows the charged spring to apply force to the linkage, which, in turn, releases the first latch, thus causing the sectionalizer to open.
A disadvantage of the Brown et al arrangement is that it is relatively complicated from a mechanical viewpoint since it requires multiple mechanical latches and a solenoid for controlling one of the latches.
The Aubrey et al patent referred to above discloses in FIGS. 4-6 a sectionalizer that is less complicated than the Brown et al arrangement in that it includes no solenoid and has only a single mechanical latch, which holds the undercenter linkage of the sectionalizer in a closed position. But the Aubrey et al sectionalizer employs a chemcial actuator for releasing this latch. This chemcial actuator, like that of the Mee et al patent discussed above, must be replaced after each operation thereof, and thus this sectionalizer is subject to the same disadvantages as discussed in connection with the Mee et al patent.